Bis(di-, tri- or tetra-substituted-cyclopentadienyl)zirconium dihalides represented by the following general formula [I] are provided, ##STR1## (wherein R.sup.1 denotes a substituent group on the cyclopentadienyl ring which is an alkyl radical of 1 to 5 carbon atoms; R.sub.2.sup.1 --C.sub.5 H.sub.3 stands for a di-substituted cyclopentadienyl radical; and X is a halogen atom). This compound, when combined with an aluminoxane repesented by the following general formula [VII], gives a high-activity catalyst for the synthesis of polyolefins, ##STR2## (wherein m is an integer of 4 to 20; and R.sup.2 denotes a hydrocarbyl radical).
提供下列一般式[I]所表示的二取代、三取代或四取代
环戊二烯基
锆二卤化物,其中:##STR1##(其中R1表示
环戊二烯基环上的取代基,为1至5个碳原子的烷基基团;R2 1-C5 H3表示二取代
环戊二烯基基团;X为卤素原子)。当此化合物与下列一般式[VII]所表示的铝烷氧化物结合时,可得到用于合成聚烯烃的高活性催化剂:##STR2##(其中m为4至20的整数;R2表示烃基基团)。